Rouded Edges Triangles
A Reuleaux triangle is a very particular geometric shape that has the ability to rotate within a square. Because of this, it's often used in complex machinery. And you're familiar with it in the real world, too: the Reuleaux triangle is the shape of a standard pencil (rather than the more traditional round or hexagonal barrels) because it's more comfortable and less likely to roll off tables. But this geometric shape is not available by default in Illustrator, and making it only requires a triangle, a circle and a few easy steps that i will show you here so you can make your own in less than 5 minutes.
Open Illustrator and make a new file at any size you want. In this case i will make mine at 1800 x 1200 px.
In the Tools Panel, select the Polygon Tool.
Click once over the Artboard to open the Polygon Tool options window.
In the Polygon Tool window set the radius to 150, the sides to 3 and click OK.
Be sure to have the Smart Guides enabled (View > Smart Guides). Select the Ellipse Tool (L) and while holding the Ctrl + Shift keys on your keyboard draw an ellipse starting from the bottom left angle of the triangle until the Smart Guide reaches the right bottom angle as shown.
With the circle still active, pick the Selection Tool (V) hold the Alt key on your keyboard and drag the circle to the right until the center of it snap onto the bottom right corner of the triangle as shown.
Again, hold the Alt key on your keyboard and drag the circle to the top until the center of it snap onto the top corner of the triangle as shown.
Go to Select > All.
Select the Shape Builder Tool.
While holding the Alt key on your keyboard, click and draw trought the shapes we don't need for the Reauleaux Triangle as shown.
Lastly, release the Alt key and simply click and draw over the remaining shapes to add them all together.